4 PTFE tubes are inserted into the top, then an M2.5 grub screw (an M3 screw can be used in a pinch, but be careful not to screw too far or you risk messing up the ends of the tubes) is screwed between them, wedging them into the opening. Don't screw more than 4 or 5mm past the opening. It will be strong enough, but if you go further, you risk crushing the ends of the tubes.
I didn't get around to updating the following picture to show an M2.5 grub screw, but it at least shows where the screw goes:
Requires an MR63ZZ bearing and a GM 4.0 micro switch. Also some M3 heat inserts and short M3 screws. You may wish to modify the exit path to suit your needs. It's currently designed to be drilled out a little to fit the entrance to an LXG lite with some PTFE sticking out the top. I suggest chasing out the hole down the middle with a drill slightly larger than your filament diameter.
Print in this orientation:
The author marked this model as their own original creation.